GB2401199A

GB2401199A - Method of operating an engine installation

Info

Publication number: GB2401199A
Application number: GB0330168A
Authority: GB
Inventors: Hans-Ernst Beyer; Frank Kastner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-01-10
Filing date: 2003-12-30
Publication date: 2004-11-03
Anticipated expiration: 2023-12-30
Also published as: US20040139796A1; FR2850432B1; GB0330168D0; DE10300592B4; US6925864B2; GB2401199B; DE10300592A1; FR2850432A1

Abstract

A method of operating an engine installation 5, with an internal combustion engine 1 and with a setting element 10 in an air feed 15 for setting an air mass to be fed to the engine, which enables simple and reliable diagnosis of leakage in the air feed. The method comprises first and second adaptations for setting the setting element 10, such as a throttle flap. The first adaptation is adapted to an actual operating state by means of a first adaptation value and is further adapted by the second adaptation by means of a second adaptation value for compensation for longer-term influencing magnitudes on the setting of the setting element. The second adaptation value is formed in dependence on a minimum first adaptation value formed in the first adaptation. A leakage in the air feed is diagnosed in dependence on the second adaptation value.

Description

2401 1 99

METHOD OF OPERATING AN ENGINE INSTALLATION

The present invention relates to a method of operating an engine installation, in particular an installation with an internal combustion engine.

It is known, in the case of an engine installation with an internal combustion engine and with a setting element in an air feed for setting an air mass to be fed to the engine, to adapt a setting of the setting element by means of a short-duration adaptation to an actual operating state and to adapt a setting of the setting element by means of a longduraton adaptation for compensation for longer-term influencing magnitudes on the setting of the setting element. In that case in the long-duration adaptation, a long-duration adaptation value for the setting of the setting element is formed in dependence on a minimum short- duration adaptation value, which is formed in the short-duration adaptation, for the setting of the setting element.

According to the present invention there is provided a method of operating an internal combustion engine with a combustion motor and with a setting element in an air feed for setting an air mass to be fed to the motor, wherein a setting of the setting element is adapted to an actual operating state by means of a short-duration adaptation and wherein a setting of the setting element is adapted by means of a long-duration adaptation for compensation for longer-term influencing magnitudes on the setting of the setting element, wherein in the long-duration adaptation a long-duration adaptation value for the setting of the setting element is formed in dependence on a minimum short-duration adaptation value, which is formed in the short-duration adaptation, for the setting of the setting element, characterized in that a leakage in the air feed pipe is diagnosed in dependence on the long-duration adaptation value.

A method exemplifying to the invention for operating an internal combustion engine has the advantage that a leakage in the air feed is diagnosed in dependence on the long- duration adaptation value. In this manner such a leakage can be realised in particularly simple manner and without additional sensors and corresponds with legal diagnostic regulations.

It is particularly advantageous if the leakage is diagnosed when the longduration adaptation value falls below a first predetermined threshold. In this manner a leakage which sets in only slowly with time can be diagnosed.

A further advantage consists in diagnosing the leakage when a difference between the long-duration adaptation value and the minimum short-duration adaptation value exceeds I a second predetermined threshold In terms of amount. In this manner there can be diagnosed a leakage which sets in temporarily, in particular abruptly.

It is also advantageous if the short-duration adaptation is carried out only if no brake pumping, i.e. brake servo operation, is present. In this manner an erroneous adaptation due to brake pumping is avoided and it is ensured that the diagnosis is not falsified by: brake pumping.

A further advantage results if the short-duration adaptation is carried out only up to a predetermined altitude. Consequently, an erroneous adaptation due to the air pressure above the predetermined altitude is prevented and it is ensured that the diagnosis is not falsified by such an erroneous adaptation.

A further advantage results if the diagnosis is undertaken only when after first starting of the combustion motor at least one long-duration adaptation value has been formed. In this I manner it is ensured that valid initial data are present for the diagnosis.

This advantage also results if the diagnosis is carried out only if the long-duration! adaptation was valid in an actual operating cycle.

It is particularly advantageous when a load of the engine is ascertained by way of an induction duct pressure. In this case the leakage does not lead to an erroneous fuel metering, so that a leakage in the air feed cannot be diagnosed on the basis of the fuel metering. However, through a method exemplifying the invention a diagnosis of the leakage in the air feed is ensured even if the engine load is ascertained only by way of an: induction duct pressure. I An example of the present invention will now be more particularly described with reference to the accompanying drawings, in which: Fig. 1 is a block circuit diagram of an engine installation in which a method exemplifying the invention can be performed; and Fig. 2 is a flow chart illustrating the steps of a method exemplifying the invention.

Referring now to the drawings there is shown in Fig. 1 an internal combustion engine 5 of, for example, a motor vehicle, the engine 5 comprising a combustion motor 1 which by way of example can be constructed as an Otto engine. Fresh air is fed to the engine by way of an air feed system 15 in the arrow direction. The air in flow direction in the system 15 initially passes an air filter 45. A compressor 50, for example an exhaust gas turbocharger, a supercharger or an electrically operated compressor, which compresses the fed air in the activated state of the compressor 50, can optionally be arranged in the system 15 after the air filter 45 in flow direction. An air mass meter 55, for example a hot- film air mass meter, can be optionally arranged after the compressor 50 in flow direction, as illustrated in Fig. 1. A setting element 10, for example a throttle flap, is arranged after this meter in flow direction. In the following it is assumed by way of example that the setting element 10 is a throttle flap. The region of the system 15 between the throttle flap and an inlet valve, which is not illustrated in Fig. 1, of the engine is also termed Induction duct 20 in the following. An induction duct pressure sensor 90 can be optionally arranged In the induction duct 20, as illustrated in Fig. 1. The injection of fuel is not illustrated in Fig. 1 and can in the case of petrol direct injection take place directly into a combustion chamber (not illustrated in Fig. 1) of the engine or indirectly into the induction duct 20. The exhaust gas resulting from combustion of the air/fuel mixture in the combustion chamber of the engine is fed by way of an exhaust valve (not illustrated in Fig. 1) to an exhaust pipe 105. A lambda probe 95, which measures the oxygen content of the exhaust gas, can optionally be arranged in the exhaust pipe 105.

Engines can have a crankcase ventilation system in which crankcase ventilation gases are fed to the intake side of the engine for combustion. A tank ventilation system can optionally also be provided, in which the tank ventilation gases are fed to the engine for combustion. In the embodiment of Fig. 1 there is provided not only a tank ventilation system, but also a crankcase ventilation system. Alternatively, also only one of the two ventilation systems, thus either the crankcase ventilation system or the tank ventilation system, could be provided. In that case distinction is made between part-load ventilation and full-load ventilation. The full-load ventilation gases are fed to the air feed system 15 after the air filter 45 in flow direction. The full-load ventilation gases are thus fed to the system 15 between the air filter 45 and the throttle flap 10. In the case of use of the air mass meter 55, the feed of the full-load ventilation gases takes place between the air filter and the air mass meter 55. In the case of use of the compressor 50, as illustrated in Fig. 1 the full-load ventilation gases are fed to the air feed system 15 between the air filter and the compressor 50. The fullload ventilation comprises a first crankcase ventilation and a first tank ventilation 35. The first crankcase ventilation 25 can be varied In its mass flow by way of a first valve 60 with an adjustable degree of opening and the first tank ventilation 35 can similarly be varied in its mass flow by way of a second valve 65 with an adjustable degree of opening. The connection of the full-load ventilation between the air filter 45 and the throttle flap 1O, In particular between the air filter 45 and the compressor 50, enables utilisation of a slight underpressure by comparison with the ambient atmospheric pressure in this section of the air feed system 15 at full load, particularly when the compressor 50 is activated. The part- load ventilation is fed to the induction duct 20 and comprises, in the embodiment of Fig. 1, a second crankcase ventilation 30 and a second tank ventilation 40. The second crankcase ventilation 30 can be varied in its mass flow by way of a third valve 70 with an adjustable degree of opening and the second tank ventilation 40 can similarly be varied in its mass flow by way of a fourth valve 75 with an adjustable degree of opening. The feed of the part-load ventilation to the induction duct 20 is based on the fact that at part load an underpressure by comparison with ambient atmospheric pressure prevails in the induction duct 20. At full load, thereagainst, either ambient atmospheric pressure or, particularly in the case of use of the compressor 50, in the activated state thereof an excess pressure by comparison with ambient atmospheric pressure prevails in the induction duct 20 According to Fig. 1 a rotational speed sensor 100 is arranged at the engine and ascertains, for example from the rotation of the crankshaft (not illustrated in Fig. 1) of the engine an actual value for engine speed. The actual value for the engine speed is fed from the rotational speed sensor 100 to an engine control 85. In addition, the measurement signal of the induction duct pressure sensor 90 and thus a measurement value for the induction duct pressure is fed to the engine control 85. A measurement signal of the air mass meter 55 and thus a measurement value for the air mass or air mass flow fed to the engine can also be supplied to the engine control 85. The engine control 85 separately controls the degree of opening of each of the valves 60, 65, 70 and 75, as illustrated in Fig. 1. The engine control 85 moreover controls the degree of opening or the setting of the throttle flap 10. Furthermore, the engine control 85 controls, in a manner which is not illustrated, the admetering of the fuel and the ignition instant of the engine.

A defect of the crankcase ventilation system and/or of the tank ventilation system leads on the one hand to the escape of harmful hydrocarbon emissions into the environment and on the other hand to a changed operating point of the engine, in particular in an idling operating state, due to leakage air. With respect to the changed operating point of the engine a leakage in the full-load ventilation is non-critical in the case of use of the air mass meter 55, since the additional fresh air feed caused by the leakage is measured by the air mass meter 55. In the case of a lambda regulation, which is implemented in the engine control 85, for tracking a predetermined lambda target value by a lambda actual value ascertained from the measurement value of the lambda probe 95, the engine control 85 can determine from the air mass flow measured by the air mass meter 55 the requisite fuel quantity to be injected in order to achieve the predetermined lambda target value. If no air mass meter is used or the measurement result of the air mass meter 55 is not evaluated, the load of the engine or the degree of filling of the engine combustion chamber is ascertained from the measurement value of the induction duct pressure sensor 90. In that case, the measured induction duct pressure takes into consideration not only a leakage in the full-load ventilation, but also a leakage in the part-load ventilation. Thus, In the case of use of the induction duct pressure sensor 90 for determining the load state of the engine notwithstanding a leakage in the full-load ventilation and/or in the part-load ventilation the correct value for the fuel quantity, which is to be injected, is ascertained in the engine control 85 from the degree of filling, which is derived from the measured induction duct pressure, In order to set the predetermined lambda target value.

If the induction duct pressure sensor 90 is not used or its measurement value is not evaluated and the air mass fed to the engine combustion chamber is determined by way of the air mass meter 55, in the case of a leakage in the part-load ventilation this has the consequence that the air fed to the combustion chamber by way of the leakage cannot be measured by the air mass meter 55 and thus an erroneous admetering of the injection fuel quantity takes place, since the fuel admetering is carried out principally on the basis of the air mass ascertained by the air mass meter 55. There is then a deviation between the ratio of the air mass measured by the air mass meter 55 and the injected fuel mass and the ratio, which is detected by the lambda probe 95, of the combusted air/fuel mixture. A leakage in the part-load ventilation can be diagnosed with the help of this deviation.

In the described embodiment there shall be understood by leakage of the full-load ventilation a leakage in the air feed system 15 in flow direction in front of the air mass meter 55 and, in the absence thereof, in front of the throttle flap 10, in the first crankcase ventilation 25 in flow direction after the first valve 60 and/or in the first tank ventilation 35 in flow direction following the second valve 65. The flow directions are always indicated in Fig. 1 by arrows.

In this embodiment there shall be understood by a leakage of the partload ventilation a leakage in the induction duct 20, a leakage in the second crankcase ventilation 30 in flow direction behind the third valve 70 and/or a leakage in the second tank ventilation 40 after the fourth valve 75 in flow direction.

Through a method exemplifying the invention there is made possible a diagnosis which reliably recognises leakages in the part-load ventilation without requiring for this purpose use of the air mass meter 55. As leakage there is then to be understood in the described embodiment, for example, also a hose which has detached in one of the crankcase ventilations 30 or in one of the tank ventilations 40. In the following, for description of the method there is considered by way of example the part-load ventilation. This is described for an engine operational state in which a regulation of filling charge in idling is active.

This can be any engine operational state, particularly an idling operational state. The idling charge regulation has, as is known, the task of tracking a target value by the actual value of the engine speed. The throttle flap 10 serves as a setting element. The control and degree of opening or the setting of the throttle flap 10 are formed in the engine control 85. In the case of faulty behaviour of the part-load ventilation due to, for example, a leakage in the induction duct 20, in the second crankcase ventilation 30 in flow direction after the third valve 70 and/or in the second tank ventilation 40 in flow direction after the fourth valve 75 the throttle flap 10 has to be closed again in the idling operational state in order to regulate-in the target value of the engine speed. A measure for the leakage is thus the setting magnitude, or the degree of opening, for the throttle flap 10 generated in the engine control. The larger the leakage, the smaller the degree of opening of the throttle flap 10, since the necessary combustion air is fed to the engine by way of the leakage past the throttle flap 10.

Adaptations for control of the throttle flap 10 by carrying out fine adaptations to the respective vehicle or engine are known. In that case distinction is made between short- duration adaptation and long-duration adaptation. With the short-duration adaptation the setting of the throttle flap 10 is to be adapted relatively quickly to the respective actual operating state so as to assist the stability of the idling charge regulator. Through the long- duration adaptation a setting of the throttle flap 10 is to be adapted in a manner providing compensation for longer-term influencing magnitudes on the setting of the throttle flap 10. The long-duration adaptation undertakes, in stable environmental conditions, a long-duration adaptation of the idling charge regulator with respect to control of the setting of the throttle flap 10. Stable environmental conditions are present, for example, when the engine temperature and the induction air temperature lie in a predetermined range, when an air-conditioning installation is in use and the instantaneous demand thereon does not exceed a predetermined value and when a power-assisted steering is not against an end stop. The long-term influencing magnitudes on the setting of a throttle flap 10 can be, for example, coking of the throttle flap 10 and in a long-term change in engine load in the idling state. The long- duration adaptation in other words serves the purpose of balancing out divergences between the engine and the control of the throttle flap 10 and compensating for the influence of contamination of the throttle flap 10, such as arise during the operating life of the engine.

In the following, the sequence of the method is described by way of example on the basis of the flow chart according to Fig. 2. After start of the program the engine control 85 checks at a program point 200 whether the long-duration adaptation was freed in the actual operating cycle of the engine combustion motor 1 and, if this drives a motor vehicle, in actual travel of the vehicle. For release of the iong- duration adaptation stable environmental conditions are, as described, necessary. Such conditions are, as described, that the motor temperature and the induction air temperature each lie in a predetermined range, the torque required by an optionally present air-conditioning installation does not exceed a predetermined value and an optionally present power- assisted steering does not bear against a stop. Moreover, release of the long-duration adaptation can be linked with the criteria that no raising of the target value of the engine speed was activated, that the short- duration adaptation is released, that in the case of a vehicle this is travailing and no erroneous measurement signal for travel speed is present, that a predetermined delay time after starting of the engine has expired and that an adaptation integrator for the short-duration adaptation is not limited to a maximum value. If the engine control 85 establishes at the program point 200 that the stated conditions for release of the long-duration adaptation are all fulfilled, then there is continuation to a program point 205, but otherwise branching to a program point 220.

At the program point 205 the engine control 25 detects, for example by means of a measurement signal of an ambient atmosphere pressure sensor (not illustrated in Fig. 1), whether the engine is operated at a height above sea level which does not exceed a predetermined altitude. If this is the case, then there is continuation to a program point 210, but otherwise branching to the program point 220. Exceeding of the predetermined height can lead to falsification of the short-duration adaptation.

At the program point 210 the engine control 85 checks whether brake pumping is absent.

if this is so, there is continuation to a program point 215, but otherwise branching to the program point 220. Brake pumping is detected by the engine control 85 on actuation of a brake pedal of the motor vehicle. In this case, the brake servo pumps air into the Induction duct so that the short-duration adaptation is falsified. If such brake pumping is not possible with the specific engine, i.e. there is no brake servo, the program point 210 can be dispensed with.

At program point 215 the engine control 85 adapts a minimum basic value ad g_min_1. In the case of this adaptation the smallest occurring value of the adaptation integrator used for the short-duration adaptation, less a height-dependent initialization value h_ad_iw, is stored as adaptation minimum basic value ad_g_min_1. This adaptation minimum basic value is a representative value for the long-duration behaviour, since long-term load changes of the engine and environmental influences, for example air temperature, influence the long-duration adaptation towards higher values and the minimum basic value has the corresponding growth potential. The height-dependent initialization value h_ad_iw can be calculated in dependence on the actual height above sea level, for example from an applied characteristic curve, on starting of the engine or at the latest at the program point 215 before ascertaining the adaptation minimum basic value ad_g_min_1.

After the program point 215 there is continuation to a program point 225.

At the program point 220 there is used, as adaptation minimum basic value ad_g_min_1, the last adaptation minimum basic value calculated in one of the preceding operating cycles of the engine. Subsequently, there is similarly continuation of the program point 225.

If at the program point 220 of the control 85 no adaptation minimum basic value ad_g_min_1 is present from a preceding operating cycle, for example because the actual operating cycle is the hrst operating cycle after starting of the engine, it can be provided that no action takes place at the program point 220 and instead thereof there is return to the program point 200.

The long-duration adaptation takes place in the motor control 85 at the program point 225.

Starting out from a last-ascertained long-duration adaptation value Iza_gw in a preceding operating cycle or from an initial long-duration adaptation value in case the actual operating cycle is the first operating cycle of the engine after starting, the engine control 85 checks at the program point 225 whether the adaptation minimum basic value ad_g_min_1 is greater by a first applicable offset than the present long-duration adaptation value Iza_gw. If this is the case, then the long- duration adaptation value Iza_gw is increased by this first applicable offset. The engine control 85 also checks at the program point 225 whether the adaptation minimum basic value ad_g_min_1 is smaller by a second applicable offset than the present long-duration adaptation value Iza_gw. If this is the case, then the long-duration adaptation value Izw_gw is reduced by the second applicable offset. Otherwise the present long-duration adaptation value Iza_gw remains unchanged.

The long-duration adaptation value Iza_gw can be limited to a maximum value LZA_GMAX. Otherwise, it can also be provided that the long-duration adaptation value Iza_gw is not smaller than 0. After the program point 225 there is continuation to a program point 230.

At the program point 230 the engine control 85 checks whether since starting of the engine a long-duration adaptation was already undertaken and a long-duration adaptation value Iza_gw was determined and stored by the engine control 85. If this is the case, then there is continuation to a program point 235, but otherwise return to program point 225.

At the program point 235 the engine control 85 checks whether in the actual operating cycle of the engine the long-duration adaptation that was undertaken was valid and whether a corresponding long-duration adaptation value Izw_gw was determined and stored by the engine control 85. The long-duration adaptation In the actual operating cycle is valid if the short-duration adaptation in the actual operating cycle was active for at least a predetermined time. If a valid long-duration action of the engine control 85 was thus established at program point 235 then there is continuation to a program point 240, but otherwise return to the program point 235.

The diagnostic method is started at the program point 240. For that purpose the engine control 85 checks whether the actually valid, stored long-duration adaptation value Izw_gw has fallen below a first predetermined threshold. If this is so, then there is continuation to a program point 250, but otherwise branching to a program point 245.

At the program point 250 the engine control 85 detects any leakage of the part-load ventilation which has effect in only slowly. In the case of such a leakage setting in only slowly, only a small difference arises between the adaptation minimum basic value ad_g_min_1 and the long- duration adaptation value Iza_gw. This leads to a lowering of the long- duration adaptation value or Iza_gw at the program point 225. In the case of a leakage setting in only slowly, for example due to a porous hose in the second crankcase ventilation 30 or in the second tank ventilation 40 or due to a crack in the induction duct 30, in the second crankcase ventilation 30 or in the second tank ventilation 40, the long- duration adaptation value Iza_gw is constantly reduced in the longer term until it falls below the first predetermined threshold and the leakage slowly coming into effect can be diagnosed. After the program point 250 there is similarly continuation to the program point 245.

At the program point 245 the engine control 85 forms a difference A = Iza_gw - ad_g_min_1. Subsequently there is continuation to a program point 255.

At the program point 255 the engine control 85 checks whether the difference A exceeds a second predetermined threshold in terms of amount. If this is so, there is continuation to a program point 260, but otherwise departure from the program.

At the program point 260 the engine control 85 detects any abrupt leakage in the part-load ventilation at which a large difference above the second predetermined threshold in terms of amount arises relatively quickly between the adaptation minimum basic value ad_g_min_1 and the longduration adaptation value Iza_gw. This leads to fault recognition in the engine control 85 at the program point 260. Due to such an abrupt leakage the adaptation minimum basic value ad_g_mn_1 very rapidly adopts smaller values than for a fault-free system. Since the short-duration adaptation seeks to provide compensation for the fault or the leakage in the part-load ventilation much more quickly than the non- duration adaptation, in the case of a very strong deviation of the adaptation minimum basic value of ad_g_min_1 from the long-duration adaptation value Iza_gw in terms of amount above the second predetermined threshold a leakage in the part-load ventilation can now be assumed.

After the program point 260 there is similarly departure from the program.

The first predetermined threshold and the second predetermined threshold can be applied in suitable manner in order to detect in good time an abrupt leakage in the part-load ventilation or a leakage, which sets in only slowly, in the part load ventilation.

The diagnosed leakage at the program point 250 or at the program point 260 can be filed in a fault memory and displayed to the driver in a combination instrument. It is also readable in workshops by means of a workshop tester.

The adaptation minimum basic value ad_g_min_1 represents a minimum shortduration adaptation value in the case of the described method.

The short-duration adaptation and thus also the long-duration adaptation are, as described, undertaken only if no brake pumping is present, in order not to falsify diagnosis of leakages in the part-load ventilation by brake pumping. This applies, as described, only if brake pumping is possible, for example by means of a brake servo. Correspondingly, as described the short-duration adaptation and thus also the lony-duration adaptation are carried out only up to a predetermined altitude in order to avoid falsification of diagnosis of leakages of the part-load ventilation at greater elevations. The program point 205 for comparison of the actual height above sea level with the predetermined height can be dispensed with if it is established that the influence of altitude on the diagnostic result is insignificant.

An erroneous adaptation in the case of rapid change from high to low altitude without intermediate adaptation is avoided by the heightdependent initialization value h_ad_iw.

The short-duration adaptation value ascertained by means of the adaptationintegrator is formed, starting from the height-dependent initialization value h_ad_iw, by addition of a predetermined start adaptation lead value and the actually valid stored long-duration adaptation value Iza_gw. The sum of these values forms the start value for the adaptation integrator of the short-duration adaptation. The minimum short-duration adaptation value is then, as described, stored as the smallest occurring value of the adaptation integrator, less the height-dependent initialization value h_ad_iw, as adaptation minimum basic value ad_g_min_1. The predetermined start adaptation lead value serves as a buffer during the warming-up phase of the engine, since after starting only a short-duration adaptation in downward direction, thus to smaller values, is permitted. Outside the warming-up phase a short- duration adaptation in upward direction is also permitted. As setting magnitude for the setting of a throttle flap 10 there is used the short- duration adaptation value which results as the output of the adaptation integrator of the short-duration adaptation. The smaller the short- duration adaptation value, the smaller the degree of opening of the throttle flap. In this manner the setting of the throttle flap takes into consideration the actual operating state. Since for the short-duration adaptation there is basing on the short- duration adaptation in the described manner, longer-term influencing magnitudes having an influence on the setting of the throttle flap are taken into consideration in formation of the short-duration adaptation value and thus for the control of the throttle flap. Through the diagnostic method fault states due to leakages can be recognised before, for example in an idling state, permanent deviations of the actual value of the engine speed from the target value arise. No additional sensor system is required for the diagnosis. Through the diagnosis it is possible to indicate to the vehicle driver the faulty state of the engine so that he or she can seek a service workshop. The diagnostic method can also be used as an independent check of a diagnosis of leakages undertaken in the described manner with the help of the air mass meter. Ultimately, legal diagnostic requirements are fulfilled by the diagnostic method.

Claims

1. A method of operating an engine installation having an internal combustion engine and seeable setting means for setting a parameter of air supplied to the engine by intake means of the installation, the method comprising the steps of carrying out a short-duration adaptation of the setting of the setting means to an actual operating state of the engine on the basis of a minimum short-duration adaptation value!and|a long-duration adaptation of the setting of the setting means to compensate for long-term influences thereon on the basis of a long- duration adaptation value dependent on the minimum short-duration adaptation value|and diagnosing leakage in the intake means in dependence on the long- duration adaptation value.

2. A method as claimed in claim 1, wherein the step of diagnosing comprises recognising the leakage when the long-duration adaptation value falls below a predetermined threshold.

3. A method as claimed in claim 1 or claim 2, wherein the step of diagnosing comprises recognising the leakage when the difference between the long-duration and minimum short-duration adaptation values exceeds a predetermined threshold amount.

4. A method as claimed in any one of the preceding claims, wherein the step of carrying out the short-duration adaptation is undertaken only when the engine installation is uninfluenced by brake servo action in a vehicle equipped with the installation.

5. A method as claimed in any one of the preceding claims, wherein the step of carrying out the short-duration adaptation is undertaken only if the engine installation is below a predetermined attitude.

6. A method as claimed in any one of the preceding claims, wherein the step of diagnosing is undertaken only if at least one long-duration adaptation value has been formed since starting of the engine.

7. A method as claimed in any one of the preceding claims, wherein the step of diagnosing is undertaken only if the long-duration adaptation has been carried out beforehand in a travel state of a vehicle equipped with the installation.

8. A method as claimed in any one of the preceding claims, comprising the step of determining the load of the engine by way of the pressure in an induction duct of the intake means.

9. A method as claimed in any one of the preceding claims, comprising the step of determining the load of the engine by way of the mass of the supplied air.

10. A method as claimed in any one of the preceding claims, wherein the step of diagnosing comprises identifying a leakage in at least one of an induction duct, engine crankcase ventilation means and fuel tank ventilator means of the intake means

10. A method as claimed in any one of the preceding claims, wherein the step of diagnosing comprises identifying a leakage in at least one of an induction duct, engine crankcase ventilation means and fuel tank ventilation means of the intake means. 1$

Amendments to the claims have been filed as follows

CLAI MS

1. A method of operating an engine installation having an internal combustion engine and gettable setting means for setting a parameter of air supplied to the engine by intake means of the installation, the method comprising the steps of carrying out a first adaptation of the setting of the setting means to an actual operating state of the engine on the basis of a first adaptation value and a second adaptation of the setting of the setting means to compensate for long-term influences thereon on the basis of a second adaptation value dependent on the first value and diagnosing leakage in the intake means in dependence on the second value.

2. A method as claimed in claim 1, wherein the step of diagnosing comprises recognsing the leakage when the second value falls below a predetermined threshold.

3. A method as claimed in claim 1 or claim 2, wherein the step of diagnosing comprises recognising the leakage when the difference between the second and first values exceeds a predetermined threshold amount.

4. A method as claimed in any one of the preceding claims, wherein the step of carrying out the first adaptation is undertaken only when the engine installation is uninfluenced by brake servo action in a vehicle equipped with the installation.

5. A method as claimed in any one of the preceding claims, wherein the step of carrying out the first adaptation is undertaken only if the engine installation is below a predetermined attitude.

6. A method as claimed in any one of the preceding claims, wherein the step of diagnosing is undertaken only if at least one second value has been formed since starting of the engine.

7. A method as claimed in any one of the preceding claims, wherein the step of diagnosing is undertaken only if the second adaptation has been carried out beforehand in a travel state of a vehicle equipped with the installation.